// Animancer // https://kybernetik.com.au/animancer // Copyright 2018-2023 Kybernetik //

#if UNITY_EDITOR
using Animancer.Editor;
using System;
using UnityEditor;
using UnityEngine;
#endif

namespace Animancer.Units
{
    /// <summary>[Editor-Conditional] Causes a float field to display using 3 fields: Normalized, Seconds, and Frames.</summary>
    /// <remarks>
    /// Documentation: <see href="https://kybernetik.com.au/animancer/docs/manual/transitions#time-fields">Time Fields</see>
    /// </remarks>
    /// https://kybernetik.com.au/animancer/api/Animancer.Units/AnimationTimeAttribute
    /// 
    [System.Diagnostics.Conditional(Strings.UnityEditor)]
    public sealed class AnimationTimeAttribute : UnitsAttribute
    {
        /************************************************************************************************************************/

        /// <summary>A unit of measurement used by the <see cref="AnimationTimeAttribute"/>.</summary>
        public enum Units
        {
            /// <summary>A value of 1 represents the end of the animation.</summary>
            Normalized = 0,

            /// <summary>A value of 1 represents 1 second.</summary>
            Seconds = 1,

            /// <summary>A value of 1 represents 1 frame.</summary>
            Frames = 2,
        }

        /// <summary>An explanation of the suffixes used in fields drawn by this attribute.</summary>
        public const string Tooltip = "x = Normalized, s = Seconds, f = Frame";

        /************************************************************************************************************************/

        /// <summary>Cretes a new <see cref="AnimationTimeAttribute"/>.</summary>
        public AnimationTimeAttribute(Units units)
        {
#if UNITY_EDITOR
            SetUnits(Multipliers, DisplayConverters, (int)units);
#endif
        }

        /************************************************************************************************************************/
#if UNITY_EDITOR
        /************************************************************************************************************************/

        /// <summary>[Editor-Only] A converter that adds an 'x' suffix to the given number.</summary>
        public static readonly CompactUnitConversionCache
            XSuffix = new CompactUnitConversionCache("x");

        private static new readonly CompactUnitConversionCache[] DisplayConverters =
        {
            XSuffix,
            new CompactUnitConversionCache("s"),
            new CompactUnitConversionCache("f"),
        };

        /************************************************************************************************************************/

        /// <summary>[Editor-Only] The default value to be used for the next field drawn by this attribute.</summary>
        public static float nextDefaultValue = float.NaN;

        /************************************************************************************************************************/

        /// <inheritdoc/>
        protected override int GetLineCount(SerializedProperty property, GUIContent label)
            => EditorGUIUtility.wideMode || TransitionDrawer.Context == null ? 1 : 2;

        /************************************************************************************************************************/

        /// <inheritdoc/>
        public override void OnGUI(Rect area, SerializedProperty property, GUIContent label)
        {
            EditorGUI.BeginChangeCheck();

            var nextDefaultValue = AnimationTimeAttribute.nextDefaultValue;

            BeginProperty(area, property, ref label, out var value);
            OnGUI(area, label, ref value);
            EndProperty(area, property, ref value);

            if (EditorGUI.EndChangeCheck())
            {
                TransitionPreviewWindow.PreviewNormalizedTime =
                    GetDisplayValue(value, nextDefaultValue) * Multipliers[(int)Units.Normalized];
            }
        }

        /************************************************************************************************************************/

        /// <summary>[Editor-Only] Draws the GUI for this attribute.</summary>
        public void OnGUI(Rect area, GUIContent label, ref float value)
        {
            var context = TransitionDrawer.Context;
            if (context == null)
            {
                value = DoSpecialFloatField(area, label, value, DisplayConverters[UnitIndex]);
                goto Return;
            }

            var length = context.MaximumDuration;
            if (length <= 0)
                length = float.NaN;

            AnimancerUtilities.TryGetFrameRate(context.Transition, out var frameRate);

            var multipliers = CalculateMultipliers(length, frameRate);
            if (multipliers == null)
            {
                EditorGUI.LabelField(area, label.text, $"Invalid {nameof(Validate)}.{nameof(Validate.Value)}");
                goto Return;
            }

            DoPreviewTimeButton(ref area, ref value, context.Transition, multipliers);

            IsOptional = !float.IsNaN(nextDefaultValue);
            DefaultValue = nextDefaultValue;
            DoFieldGUI(area, label, ref value);

            Return:
            nextDefaultValue = float.NaN;
        }

        /************************************************************************************************************************/

        private static new readonly float[] Multipliers = new float[3];

        private float[] CalculateMultipliers(float length, float frameRate)
        {
            switch ((Units)UnitIndex)
            {
                case Units.Normalized:
                    Multipliers[(int)Units.Normalized] = 1;
                    Multipliers[(int)Units.Seconds] = length;
                    Multipliers[(int)Units.Frames] = length * frameRate;
                    break;

                case Units.Seconds:
                    Multipliers[(int)Units.Normalized] = 1f / length;
                    Multipliers[(int)Units.Seconds] = 1;
                    Multipliers[(int)Units.Frames] = frameRate;
                    break;

                case Units.Frames:
                    Multipliers[(int)Units.Normalized] = 1f / length / frameRate;
                    Multipliers[(int)Units.Seconds] = 1f / frameRate;
                    Multipliers[(int)Units.Frames] = 1;
                    break;

                default:
                    return null;
            }

            var settings = AnimancerSettings.AnimationTimeFields;
            ApplyVisibilitySetting(settings.showNormalized, Units.Normalized);
            ApplyVisibilitySetting(settings.showSeconds, Units.Seconds);
            ApplyVisibilitySetting(settings.showFrames, Units.Frames);

            void ApplyVisibilitySetting(bool show, Units setting)
            {
                if (show)
                    return;

                var index = (int)setting;
                if (UnitIndex != index)
                    Multipliers[index] = float.NaN;
            }

            return Multipliers;
        }

        /************************************************************************************************************************/

        private void DoPreviewTimeButton(ref Rect area, ref float value, ITransitionDetailed transition,
            float[] multipliers)
        {
            if (!TransitionPreviewWindow.IsPreviewingCurrentProperty())
                return;

            var previewTime = TransitionPreviewWindow.PreviewNormalizedTime;

            const string Tooltip =
                "• Left Click = preview the current value of this field." +
                "\n• Right Click = set this field to use the current preview time.";

            var displayValue = GetDisplayValue(value, nextDefaultValue);

            var multiplier = multipliers[(int)Units.Normalized];
            displayValue *= multiplier;

            var isCurrent = Mathf.Approximately(displayValue, previewTime);

            var buttonArea = area;
            if (TransitionDrawer.DoPreviewButtonGUI(ref buttonArea, isCurrent, Tooltip))
            {
                if (Event.current.button != 1)
                    TransitionPreviewWindow.PreviewNormalizedTime = displayValue;
                else
                    value = previewTime / multiplier;
            }

            // Only steal the button area for single line fields.
            if (area.height <= LineHeight)
                area = buttonArea;
        }

        /************************************************************************************************************************/

        /// <summary>[Editor-Only] Options to determine how <see cref="AnimationTimeAttribute"/> displays.</summary>
        [Serializable]
        public class Settings
        {
            /************************************************************************************************************************/

            /// <summary>Should time fields show approximations if the value is too long for the GUI?</summary>
            /// <remarks>This setting is used by <see cref="CompactUnitConversionCache"/>.</remarks>
            [Tooltip("Should time fields show approximations if the value is too long for the GUI?" +
                " For example, '1.111111' could instead show '1.111~'.")]
            public bool showApproximations = true;

            /// <summary>Should the <see cref="Units.Normalized"/> field be shown?</summary>
            /// <remarks>This setting is ignored for fields which directly store the normalized value.</remarks>
            [Tooltip("Should the " + nameof(Units.Normalized) + " field be shown?")]
            public bool showNormalized = true;

            /// <summary>Should the <see cref="Units.Seconds"/> field be shown?</summary>
            /// <remarks>This setting is ignored for fields which directly store the seconds value.</remarks>
            [Tooltip("Should the " + nameof(Units.Seconds) + " field be shown?")]
            public bool showSeconds = true;

            /// <summary>Should the <see cref="Units.Frames"/> field be shown?</summary>
            /// <remarks>This setting is ignored for fields which directly store the frame value.</remarks>
            [Tooltip("Should the " + nameof(Units.Frames) + " field be shown?")]
            public bool showFrames = true;

            /************************************************************************************************************************/
        }

        /************************************************************************************************************************/
#endif
        /************************************************************************************************************************/
    }
}